Synthesis and Characterization of <i>trans</i>-[Os(en)₂py(H)]²⁺ and Related Studies

trans-[Os(en)2pyH](Otf)2, 2, is recovered from an acidic solution of trans-[Os(en)2py(H2)](OTf)2, 1, which has been subjected to one electron oxidation. The structures of both 1 and 2 have been determined by single crystal X-ray analysis. In cyclic voltammetry, 2 shows a one electron oxidation wave at 0.95 V and a one electron reduction wave at −1.2 V, neither accompanied by a signal for the reverse process. Reduction of 2 by Zn/Hg in methanol solution leads to quantitative formation of [Os(en)2(py)H2)]2+, predominantly in the trans-form. In aqueous solution, species 2 reacts rapidly with N-methylacridium ion, [MAH]+, by hydride transfer. One electron chemical oxidation of 2 to the corresponding Os(IV) is slower than that of 1 to 2 owing to the increase in coordination number when Os(IV) is produced. Treatment of 1, or the cis-form, 1‘, in DMSO by sodium t-butoxide produces mainly the corresponding isomers of the monohydrides of OsII, that derived from 1‘ is deep red in color while the trans-monohydride is colorless. Both react with [MAH]+ to form [MAH]2, and both disappear rapidly in acetone or acetonitrile, presumably by reducing the solvents. Reaction of trans-[Os(NH3)4(H2)H2O](BPh4)2, 4, in acetone-d6 as solvent with either CH3CHO or styrene leads to hydrogenation of the substrate. Reactions which compete with trans-[Os(en)2(η2-H2)(CF3SO)3]CF3SO3 release of substrate from the trans-complex before isomerization to the cis-form, required for hydrogenation to occur, result in the trans-derivative of the added solute. When H2CCHCH2SCH3 is the substrate, binding takes place at sulfur. Complete conversion to the cis-substrate isomer is observed, without hydrogenation occurring even though contact between dihydrogen and the double bond is possible

Synthesis and Characterization of Sulfur-Bridged Binuclear β-Diketonatoruthenium Complexes and a Monomeric Ruthenium Complex. Crystal and Molecular Structures of Racemic and Meso Isomers of [Ru(acac)₂(μ-topd-<i>O</i>,<i>S</i>,<i>O</i>‘)Ru(acac)₂] (acac = Acetylacetonato and topd = 3-Thioxo-2,4-pentanedione)

A new mode of binding of a β-diketone has been established. Two oxygen atoms and a sulfur atom at the γ-position of the β-diketone bind to two ruthenium atoms with the sulfur forming the bridge. A mononuclear complex has also been isolated in which the β-diketone binds through O and S atoms. The syntheses of mononuclear complex [Ru(acac)2(topd-O,S)] (1) and binuclear complexes [{Ru(acac)2}2(μ-topd-O,S,O‘)] (2, racemic form), [{Ru(acac)2}2(μ-topd-O,S,O‘)] (2‘, meso form), [{Ru(phpa)2}2(μ-topd-O,S,O‘)] (3, racemic form), and [{Ru(phpa)2}2(μ-topd-O,S,O‘)] (3‘, meso form) have been described. The crystal and molecular structures of 2 and 2‘ have been solved by single-crystal X-ray diffraction studies. Crystal data for 2 (Ru2C25H34O10S):  space group P21/n, a = 11.388(3) Å, b = 23.390(3) Å, c = 11.978(3) Å, β = 93.06(2)°, Z = 4, R = 0.056, Rw = 0.042. Crystal data for 2‘ (Ru2C25H34O10S):  space group P21/n, a = 16.281(3) Å, b = 21.195(2) Å, c = 21.465(3) Å, β = 105.75(1)°, Z = 4, R = 0.049, Rw = 0.042. The 13C NMR spectra indicate the difference between the mononuclear (1) and the binuclear complex (2‘) in their topd-CS signals for the presence of two types of bonding modes for the topd ligand. There is no difference in the electronic spectra of the meso and racemic isomers of the binuclear complexes. The X-ray photoelectron spectrum (XPS) of 1 resembles that of RuIII whereas the spectra of all of the binuclear complexes indicate the presence of both RuIII and RuII. Cyclic voltammetric studies also corroborate the findings of XPS that the monomeric complex 1 contains RuIII and all of the binuclear complexes have in them both RuIII and RuII. The electronic structures of the complexes have been discussed on the bases of photoelectron spectra, electronic spectra, and magnetic measurements and electrochemistry

Platinum(II) Complexes with Diglycine: X-ray Crystal Structure, ¹⁵N NMR Spectra, and Growth-Inhibitory Activity against Mouse Meth A Solid Tumor in Vivo

Two new dipeptide complexes of the form H[Pt(digly)Cl] (2) (H2digly = glycylglycine) and H[Pt(Hdigly)Cl2] (4) were newly prepared, and K[Pt(Hdigly)Cl2] (3) was isolated. Complex 1, K[Pt(digly)Cl], crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 25.77(1) Å, b = 4.09(2) Å, c = 16.432(9) Å, β = 103.74(4)°, and Z = 8. Complex 3 crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 8.892(5) Å, b = 11.387(4) Å, c = 9.974(4) Å, β = 105.45(4)°, Z = 4. Complex 4 crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 9.311(6) Å, b = 7.737(8), c = 15.627(4) Å, β = 105.92(3)°, Z = 4. Complex 4 has the rare iminol type H2digly coordinating to Pt. The 15N chemical shifts and the coupling constants of the deprotonated coordinated amide N were obtained for the first time for these complexes. These amide peaks showed almost no coordination shift compared with the large coordination shift of the amine nitrogen. The coupling constants between Pt and deprotonated nitrogen for K[Pt(Hdipep)Cl2] were larger than those for K[Pt(dipep)Cl]. The growth inhibition assays of K[Pt(digly)Cl], K[Pt(Hdigly)Cl2], and cis-diamminedichloroplatinum(II) (cisplatin) against methylcholanthrene-induced Meth A fibrosarcoma (Meth A) solid tumor transplanted in BALB/c mice were measured. In mice, 35.9% of slight growth inhibition was observed in the group administered with K[Pt(digly)Cl] (dose of 26 mg/kg/day), and 40.6% in the group administered with K[Pt(Hdigly)Cl2] (dose of 52 mg/kg/day), and 45.3% cisplatin (dose of 10 mg/kg/day). The side effects related to the decrease in body weight are milder than that of cisplatin. Their toxicity against normal mouse bone marrow cells was measured. All of them exhibited toxicity against bone marrow cells, but K[Pt(digly)Cl] and K[Pt(Hdigly)Cl2] had only 1/10 the toxicity of cisplatin